Known low density ceramic particles, such as cellulated glass particles, are either weak or will absorb fluid with time. Plastic coatings may alleviate these problems, although such coatings are themselves uneconomical and are not useful at elevated temperatures.
Commercially available glass microbubbles are generally limited to a maximum particle size of about 180 micrometers; while other low density ceramic particles usually are not available in sizes smaller than 840 micrometers.
There is a need for strong low density ceramics which will not absorb fluid over time and yet which avoid the high temperature instability problems of plastic coatings. There is also a need for such spheroids in the size range of 180 to 840 micrometers. Some applications for low density, high strength ceramic spheroids are proppants, fillers for low density plastics, filter media, and in linings for smoke stacks.